Europaisches Patentamt J European Patent Office 00 Publication number: 0 345 042 Office europeen des brevets A2
EUROPEAN PATENT APPLICATION
Application number: 89305485.8 S) IntCI.4: B 01 D 19/04
Date of filing: 31.05.89
® Priority: 02.06.88 GB 8813018 (72) Inventor: Reed, Kenneth Gordon Steenweg OP Leuven 65 @ Date of publication of application : B-1980Tervuren (BE) 06.12.89 Bulletin 89/49 Godwin, Allen David Avenue de I'Orangerie 9 @ Designated Contracting States : B-1410 Waterloo (BE) AT BE CH DE ES FR GB GR IT LI LU NL SE Geiregat, Nancy Madeleine Michele © Applicant: EXXON CHEMICAL PATENTS INC. Kappellestraat110B1 200 Park Avenue B-9800Deinze (BE) Florham Park New 07932 Jersey (US) Hentges, Steven George 1012 Stoneleigh Drive Baton Rouge Louisiana 70808 (US)
@ Representative: Bawden, Peter Charles et al EXXON CHEMICAL LIMITED EXXON CHEMICAL TECHNOLOGY CENTRE PO Box 1 Abingdon Oxfordshire OX13 6BB (GB)
(§4) Defoamers and their use. (g) Finely divided polyethylene waxes having terminal acetyl groups are effective defoamers which may be used both for defoaming and antifoaming. For this purpose they are formu- lated as liquid compositions comprising a suspension of the wax in an organic liquid containing appropriate surfactants and may be used as emulsions or solutions in hydrocarbon solvents.
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Bundesdruckerei Berlin EP 0 345 042 A2
Description DEFOAMERS AND THEIR USE
This invention relates to defoamers and to their production and use. Defoamers are used in a wide variety of industries. They function both as antifoamers, to prevent build-up of 5 foam, and as defoamers to destroy foams which have already formed. They are also used as de-aerating agents to accelerate the escape of entrapped air. The term "defoamer" is used to cover materials which have either antifoaming or defoaming efficiency or both. When used in "antifoaming", i.e. to prevent foam formation, the defoamer is added to the liquid which is liable to foam before any foam formation takes place. The efficiency of a defoamer in this context is measured by its effectiveness in preventing or minimising foam 10 formation. The term "defoaming" refers to the ability of a defoamer which shows good antifoaming activity may be expected to show also good defoaming activity, this is by no means always the case, and a defoamer may be a good antifoaming agent or a good defoaming agent without also being respectively a good defoaming agent or a good antifoaming agent. Known defoamers may be supplied as solutions, suspensions, emulsions or as solids. The most effective 15 and widely-used defoamers are however suspensions of finely-divided solid particles dispersed in an organic, often hydrocarbon, medium although there is a trend to use emulsion based products to avoid the environmental problems associated with the use of the hydrocarbon medium. Defoamers based on suspensions of finely-divided ethylene bis-stearmide particles in an organic medium are very widely used in paper-pulp processing, and paper manufacture. Such defoamers generally consist of a 20 suspension of finely-divided ethylene bis-stearmide particles in a hydrocarbon medium which has dissolved therein one or more surfactants which act as emulsifying and spreading agents. These compositions are effective in a wide variety of circumstances, but ethylene bis-stearmide is an expensive material and there is a need for cheaper defoamers. Indeed, in some cases it is preferable to use a relatively large quantity of a cheap, relatively inactive defoamer rather than a small quantity of an expensive but highly active defoamer, even 25 though the overall cost may be approximately the same, because in many instances it is easier to control the use of relatively large amounts of defoamer rather than small amounts which must be accurately measured. The present invention is based on the discovery that polyethylene waxes having terminal acetyl groups are very effective defoamers. When correctly formulated, they are in many contexts as effective as ethylene bis-stearamide, with the important advantage that they are much cheaper; they may also be used in emulsion 30 based defoamer systems. The use of these waxes enables emulsion defoamers in which the wax is the only active defoamer component unlike previous wax based emulsion defoamers which generally contain additional active defoamer material. The present invention accordingly provides a method for suppressing or preventing foam which comprises adding to a foamed or foamable liquid an effective amount of a finely-divided polyethylene wax having terminal 35 -COCH3 groups and containing 50-400 carbon atoms per molecule. Such polyethylene waxes are normally supplied and used in the form of a liquid defoamer composition comprising a suspension of the finely-divided solid polyethylene wax in an organic liquid carrier, e.g. a petroleum or other hydrocarbon oil or a fluid synthesised by the oxo-process, which has dissolved therein one or more surfactants effective as emulsifying and spreading agents. 40 The solid polyethylene waxes used in the present invention are known materials which are described for example in United States Patent No. 4698450. They are made by the polymerisation of ethylene in the presence of acetaldehyde as chain transfer agent in the way described in the said patent. A variety of grades of such waxes are commercially available having molecular weights ranging from about 800 to about 5,000, and a blend of such waxes may also be used. The defoamer compositions of the present invention usually contain 1 to 15
The new defoamer compositions are conveniently made by mixing the specified ingredients. Preferably, the ketonic polyethylene is dissolved in the carrier at elevated temperature and the homogeneous mixture is then quickly cooled, e.g. to 0° C. This causes the ketonic polyethylene to precipitate out in the form of solid particles of the required particle size. Such compositions have, however, sometimes an inadequate shelf-life for some purposes. Shelf-life can be substantially improved, and the defoaming activity often increased, by homogenising the mixture. The usual industrial equipment may be used for this purpose, e.g. a Gaulin homogeniser, using a pressure of, e.g., 500 bars. During the homogenisation, the temperature of the mixtures typically reaches about 35° C. The surfactants are preferably dissolved in the carrier before the ketonic polyethylene is added, but may, if desired, be added later. 10 The new defoamer composition may contain, in addition to the ingredients already mentioned, a small proportion of other constituents as used in known defoamers, e.g. finely-divided hydrophobised silica and/or a silicone oil. Such additives tend however to increase the overall cost of the defoamer composition and are not therefore desirable where cost is a prime consideration, e.g. in large-scale uses. Although the preferred compositions in accordance with the invention consist of the ketonic polyethylene 15 dispersed in an organic carrier, it is possible to make an oil-in-water or water-in-oil emulsion defoamer in which the finely-divided ketonic polyethylene and the organic carrier are dispersed in water or water is dispersed in the organic carrier. Oil-in-water emulsions can be advantageous where the defoamer is to be substantially diluted before use since for environmental and cost reasons water is the preferred diluent. The ketonic polymer may be the only particulate defoamer in those systems which are efficient, stable, of long life and low 20 viscosity. In the following examples, the particulate active defoamer may be any one of the following ketonic polyethylene waxes:
25 ECEA-1 ECEA-2 ECEA-3 ECEA-4
Molecular weight 800 4850 1100 1100 30
Carbon chain length 52 350 78 78
Density (g/ml) 0.948 0-950 0.950 35
Vicat softening point ) 102 65 68 ASTM D1525 (*C) ) 40
Ring & ball softening ) 119 115 112 point, ASTM E 28 (°C) ) 45
Viscosity at 121 °C, ASTM D 3236 ) 1200 27 27 50 (mPa.S) )
* ECEA-1 is a paste at room temperature 55
ECEA-3 is similar to ECEA-4 but is manufactured to higher specifications than ECEA-4 and therefore gives greater reproducibility of results. 60 Other ketonic polyethylene waxes could be substituted for these materials. The following examples illustrate the invention:
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EXAMPLE 1
Component Amount (wt%) Participate active 2.5 defoamer 10 Polyethyleneglycol 400 5.0 dioleate Acropol 35/7 ethylene 5.0 oxide Carrier 87.5 15 Acropol 35/7 is a Ci 3-1 5 branched chain alcohol polyoxyethylenated with 7 molecular proportions of ethylene oxide.
20 All the components were heated together with slow stirring until a homogeneous solution was obtained. The mixture was then cooled in an ice-bath and left without stirring until the temperature was about 10°C. The mixture was allowed to warm to room temperature before use. With all the particulate active ingredients tested, formulations efficient with respect to both antifoaming and defoaming were prepared. In almost all cases, formulations in which the carrier was MD-OC-H performed 25 better than equivalent formulations in which Stanco 90 (a hydrocarbon oil) was the carrier. Defoaming efficiency could be improved by adding 0.1 wt% of a silicone oil to the formulation, but the same silicone oil had an adverse effect on antifoaming efficiency. Homogenisation improved the efficiency and shelf life of the formulation in almost every case.
30 EXAMPLE 2
COMPOSITION 35
Component Amount (wt0/o) A Carrier 2.5 40 A Particulate active 2.5 defoamer A Plexol 956 2.0 B Carrier 23.0 C Carrier 11.0 45 CHydrophobic silica in 8.0 oil C Acropol 35/7 ethylene 1 .5 oxide C Water 49.4 50 D Silicone oil F 11 1/500 0.1 Plexol 956 is a metallic salt of a sulphonated aromatic hydrocarbon used as a dispersing agent.
55 All the "A" components were heated together until melted and dissolved. The mixture was kept molten for 15 minutes, and then added in the molten state to "B" which had been cooled in an ice-bath to about 5°C, with vigorous stirring. The "C" components were then added separately to "A + B" with stirring, adding the water last. The mixture was homogenised at 25°C. Component "D" was added to components "A+B + C" with stirring for 15 minutes. The product is a water-in-oil emulsion. 60 This formulation using MD-OC-H as carrier and ECEA-1 as the particulate active ingredient showed good antifoaming efficiency, and a shelf life in excess of 43 days. Homogenising the formulation gave only a slight improvement in initial efficiency and in shelf life. The benefit of homogenisation is in this case only marginal.
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EXAMPLE 3
COMPOSITION
Component Amount (wt%) Participate active 6.0 10 ingredient Witcolate 35/30 1.0 Silcolapse 430 0.5 Nonylphenol/8 ethylene 5.0 oxide 15 Exxsol D 100 S 5.5 Carrier 82.0 Witcolate 35/30 is a 30% solution in water of the sodium salt of the sulphate of C13-15 branched 20 chain alcohol polyoxyethylenated with 3 molecular proportions of ethylene oxide. Silcolapse 430 is a silicone-based anti-foaming compound. 25 Exxsol D100S is a hydrocarbon oil complying with BGA requirements.
All the ingredients except the nonylphenol/ethylene oxide condensate and the Exxsol D 100 S were mixed. This mixture was homogenised, then heated to 60° C and cooled quickly to room temperature. The 30 nonylphenol/ethylene oxide condensate was added with stirring and the viscosity checked. Lastly, the Exxsol D 100 S was added with stirring. All defoamers based on this formulation were prepared by the standard method but without homogenisation. It is likely that some of the poor results obtained when using Stanco 90 as the carrier would have been improved by homogenisation. Excellent results were obtained without homogenisation when using 35 MD-OC-H as the carrier, as shown below:
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45
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Antifoaming effects
Carrier Particulate Initial Shelf life, active Antifoam- Good ing perfor- mance (days) Stanco 90 ECEA-1 Poor/Poor < 1 10 Stanco 90 ECEA-2 Medium/ < 1 poor Stanco 90 ECEA-3 Poor/poor < 1 MD-OC-H ECEA-1 Poor/good 49 + MD-OC-H ECEA-2 Poor/good NA 15 MD-OC-H ECEA-3 Good/good 46 + Defoaming Effects
Carrier Particulate Initial Shelf life, 20 active Defoaming Good defoaming (days) Stanco 90 ECEA-1 Medium/ <1 medium 25 Stanco 90 ECEA-2 Medium/ <1 poor Stanco 90 ECEA-3 Medium/ <1 medium 30 MD-OC-H ECEA-1 N/A 17+ (G/G) MD-OC-H ECEA-3 Good/good 22+ (G/G) Antifoaming code : Poor- >5 cm foam formed in 3 minutes 35 Medium - 1
The use of MD-OC-H in place of Stanco 90 enabled defoamer formulations efficient with respect to both antifoaming and defoaming to be prepared without homogenisation. 50
EXAMPLE 4
55 COMPOSITION
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Component Amount (wt%) 1. Carrier 10 2. Particulate active 40 defoamer 3. Hexylene glycol 2 3. Butyl cellosolve 3 3. Dowanoi DPM 5 4. Water 35.5 5. Diethanolamine 1.5 *° 6. Isopropanol 3 Dowanoi DPM is dipropylene glycol monomethyl ether. 15 Components "1", "2" and "3" were heated together with mixing until a homogeneous melt was formed. Warm component "4" at about 32° C was added slowly to "1 +2+3" with vigorous mixing. Component "5" was added to "1 +2+3+4" and the mixture was heated to about 35°C while stirring. The resulting mixture was cooled to below 30° C, component "6" was added and mixed well in to give a hazy,. amber microemulsion. The use of ECEA-1 as the defoamer together with MD-OC-H as carrier produced a heterogeneous defoamer 20 with excellent antifoaming properties. The results were:
Antifoaming efficiency 25 Carrier MD-OC-H Particulate active ECEA-1 Antifoaming No foam at all after 3 efficiency - time to minutes generate 45 cm of foam 30
Claims 35
1 . A method of suppressing or preventing foam which comprises adding to a foamed or foamable liquid an effective amount of a finely divided polyethylene wax having terminal -COCH3 groups and containing 50-400 carbon atoms per molecule. 2. A liquid defoamer composition comprising a suspension of a finely divided polyethylene wax having 40 terminal -COCH3 groups and containing 50-400 carbon atoms per molecule in an organic liquid carrier which has dissolved therein one or more surfactants effective as emulsifying and spreading agents. 3. A composition according to claim 2 in which the said polyethylene wax has been made by polymerization of ethylene in the presence of acetaldehyde as chain transfer agent. 4. A composition according to claim 2 or 3 in which the carrier is a mixture of C1 6-22 aliphatic ethers and 45 ether-alcohols, optionally associated with a minor proportion of corresponding alcohols of 8 to 1 1 carbon atoms. 5. A composition according to any one of claims 2 to 4 in which the surfactants are non-ionic or anionic surfactants or both. 6. A composition according to any one of claims 2 to 5 which also contains hydrophobized silica as an 50 additional defoamer. 7. A composition according to any one of claims 2 to 6 containing 1 to 15% by weight of the said polyethylene wax. 8. A composition according to any one of claims 2 to 7 which has been homogenized. 9. A composition according to any one of claims 2 to 8 in which the composition is an aqueous 55 emulsion. 10. A composition according to claim 10 in which the polyethylene wax is the only active defoamer present. 1 1 . A composition according to claim 2 substantially as described in any one of the foregoing Examples. 12. A method according to claim 1 in which the polyethylene wax is used in the form of a composition 60 according to any one of claims 1 to 1 1 .
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